1. Field of the Invention
The present invention relates to the field of intraocular lens replacement and, more particularly, to an intraocular lens which comprises a multitude of optical surfaces.
2. Description of the Related Art
Artificial intraocular lenses, used to replace damaged or diseased natural lenses in the eye, have been widely accepted in the last several decades. Typically, such intraocular lenses comprise some type of optical element and a support, or haptic, coupled thereto for properly positioning and centering the intraocular lens within the eye. Previously, many such lenses were made from polymethylmethacrylate (PMMA), a hard plastic composition. More recently the use of a soft, biocompatible material, such as silicone, to manufacture the lenses is more common. Silicone lenses have the advantage of being lighter in situ than PMMA lenses, and because they are flexible, they can be folded or rolled to reduce their size during implantation into the eye in accordance with conventional surgical procedures.
A technique that has gained wide acceptance for the removal of the diseased or damaged native lens is called phacoemulsification. The phacoemulsification process is very advantageous because of the extremely small incision required to perform the technique. The incision can be as small as 2 mm in length. It is desirable to insert an artificial intraocular lens into the patient's eye to replace the native lens of the eye after the phacoemulsification procedure has been completed. With the latest advances in surgical procedures performed on the lens capsule, such as a capsulorexis procedure, it is possible to remove the native lens of the eye while maintaining the lens capsule almost entirely intact. The capsulorexis procedure enables a small curvilinear tear to be made in the lens capsule through which the artificial lens is implanted. The small opening in the lens capsule through which the intraocular lens is loaded and pushed further enhances the desirability of a pliable lens that can be inserted into the small capsulorexis opening. By maintaining the lens capsule intact and inserting the artificial lens into the lens capsule, a more natural lens replacement can be achieved. It is desirable to enable the insertion of the intraocular lens into the eye without requiring the elongation of either the phacoemulsification incision or the capsulorexis opening.
A lens injector is traditionally used to insert a single-piece intraocular lens, which is loaded into the injector and then inserted into the eye. The use of a lens injector to insert a compressed lens is desirable because the small phacoemulsification incision does not require elongation. In addition, the insertion procedure is significantly simplified by the loading and insertion features of an intraocular lens injector. In addition, the entire lens is contained within an insertion tube until the lens is injected into the lens capsule, thereby reducing the likelihood of damaging the surrounding eye tissue while the lens is being inserted. The simplification of the insertion procedure utilizing an intraocular lens injector has increased the frequency of their use. As the use of lens injectors for the insertion of an intraocular lens has increased, the demand for single-piece intraocular lens designs, which are compatible for use with lens injectors, has also increased.
In order to reduce trauma to the surrounding eye tissue caused by the lens injector, it is desirable that the diameter of the insertion tube of the injector be minimized. However, the thickness of the intraocular lens that is loaded, rolled and pushed through the injector is often the limiting factor in the intraocular lens injector design, as the insertion tube must be able to contain the entire lens in its loaded state. Thus, in order to enable the use of a smaller intraocular lens injector, the thickness of the intraocular lens itself must be reduced without altering the optical properties of the lens.
Further, it is desirable to provide an intraocular lens which can be adapted to correct a number of vision related problems. For example, over 30% of Americans over the age of 75 are affected by age-related macular degeneration (AMD). Further, age-related macular degeneration has become the leading cause of vision loss among the elderly. Age-related macular degeneration is a disease that effects the retina in the eye of older adults, causing central visual field loss which can result in reduced visual acuity. Other diseases of the retina, such as retinitis pigmentosa, cause portions of the retina to become non-functional. Therefore, it would be advantageous to develop an intraocular lens that could enhance the vision of patients who suffer for age-related macular degeneration and other retina related visual impairments. Finally, many intraocular lens patients complain about their inability to focus on both near and distant objects. It would be desirable to provide an intraocular lens that would enable an intraocular lens patient to focus on both close and distant objects.